Stamped by machine on a writable compact disk is a wobbled groove. The groove provides means for tracking on the disk while writing or reading data that is written in the groove. The wobbled groove, which is a frequency modulated signal after detection and processing, contains addressing and other information that is necessary for the write and read processes of the CD writer/reader.
Information is coded in a series of blocks, each of said blocks comprising 42 bits: four bits of a sync mark, eight bits of "minutes", eight bit of "seconds", eight bits of "frames", and fourteen bits of "CRC" (cyclic redundancy check). The sync marks are used to produce sync signals and these sync signals perform the following functions: (1) They indicate that at a particular location the prerecorded address information is to follow and this information is used to tell the writer/reader where the optical head is operating on the disk. (2) The sync mark establishes a reference point on the compact disk to begin a write or read sequence.
In order to work efficiently, the microprocessor which controls the writer/reader needs to be provided with an uninterrupted synchronization signal, free of invalid or missing synchronization pulses. This is obviously more critical with high speed writers. For those writers, there is an increased likelihood of noise in the detected signals which will cause synchronization marks stamped on the disk to either not be detected or to be falsely detected.